The fabrication of microelectronic components from a microelectronic workpiece, such as a semiconductor wafer substrate, polymer substrate, etc., involves a substantial number of processes. For purposes of the present application, a microelectronic workpiece is defined to include a workpiece formed from a substrate upon which microelectronic circuits or components, data storage elements or layers, and/or micro-mechanical elements are formed. There are a number of different processing operations performed on the microelectronic workpiece to fabricate the microelectronic component(s). Such operations include, for example, material deposition, patterning, doping, chemical mechanical polishing, electropolishing, and heat treatment.
Material deposition processing involves depositing or otherwise forming thin layers of material on the surface of the microelectronic workpiece. Patterning provides selective deposition of a thin layer and/or removal of selected portions of these added layers. Doping of the semiconductor wafer, or similar microelectronic workpiece, is the process of adding impurities known as “dopants” to selected portions of the wafer to alter the electrical characteristics of the substrate material. Heat treatment of the microelectronic workpiece involves heating and/or cooling the workpiece to achieve specific process results. Chemical mechanical polishing involves the removal of material through a combined chemical/mechanical process while electropolishing involves the removal of material from a workpiece surface using electrochemical reactions.
Numerous processing devices, known as processing “tools,” have been developed to implement one or more of the foregoing processing operations. These tools take on different configurations depending on the type of workpiece used in the fabrication process and the process or processes executed by the tool. One tool configuration, known as the LT-210C™ processing tool and available from Semitool, Inc., of Kalispell, Mont., includes a plurality of microelectronic workpiece processing stations that are serviced by one or more workpiece transfer robots. Several of the workpiece processing stations utilize a workpiece holder and a process bowl or container for implementing wet processing operations. Such wet processing operations include electroplating, etching, cleaning, electroless deposition, electropolishing, etc. In connection with the present invention, it is the electrochemical processing stations used in the LT-210C™ that are noteworthy. Such electrochemical processing stations perform the foregoing electroplating, electropolishing, anodization, etc., of the microelectronic workpiece. It will be recognized that the electrochemical processing system set forth herein is readily adapted to implement each of the foregoing electrochemical processes.
In accordance with one configuration of the LT-210C™ tool, the electrochemical processing stations include a workpiece holder and a process container that are disposed proximate one another. The workpiece holder and process container are operated to bring the microelectronic workpiece held by the workpiece holder into contact with an electrochemical processing fluid disposed in the process container. When the microelectronic workpiece is positioned in this manner, the workpiece holder and process container form a processing chamber that may be open, enclosed, or substantially enclosed.
Electroplating and other electrochemical processes have become important in the production of semiconductor integrated circuits and other microelectronic devices from microelectronic workpieces. For example, electroplating is often used in the formation of one or more metal layers on the workpiece. These metal layers are often used to electrically interconnect the various devices of the integrated circuit. Further, the structures formed from the metal layers may constitute microelectronic devices such as read/write heads, etc.
Electroplated metals typically include copper, nickel, gold, platinum, solder, nickel-iron, etc. Electroplating is generally effected by initial formation of a seed layer on the microelectronic workpiece in the form of a very thin layer of metal, whereby the surface of the microelectronic workpiece is rendered electrically conductive. This electro-conductivity permits subsequent formation of a blanket or patterned layer of the desired metal by electroplating. Subsequent processing, such as chemical mechanical planarization, may be used to remove unwanted portions of the patterned or metal blanket layer formed during electroplating, resulting in the formation of the desired metallized structure.
Electropolishing of metals at the surface of a workpiece involves the removal of at least some of the metal using an electrochemical process. The electrochemical process is effectively the reverse of the electroplating reaction and is often carried out using the same or similar reactors as electroplating.
Anodization typically involves oxidizing a thin-film layer at the surface of the workpiece. For example, it may be desirable to selectively oxidize certain portions of a metal layer, such as a Cu layer, to facilitate subsequent removal of the selected portions in a solution that etches the oxidized material faster than the non-oxidized material. Further, anodization may be used to deposit certain materials, such as perovskite materials, onto the surface of the workpiece.
As the size of various microelectronic circuits and components decreases, there is a corresponding decrease in the manufacturing tolerances that must be met by the manufacturing tools. In connection with the present invention as described below, electrochemical processes must uniformly process the surface of a given microelectronic workpiece. Further, the electrochemical process must meet workpiece-to-workpiece uniformity requirements.
Electrochemical processes may be conducted in reaction chambers having either a single electrode or multiple electrodes. Where a single-electrode reaction chamber is used, improving the level uniformity achieved by the process often involves manual trial-and-error modifications to the hardware configuration of the reaction chamber. For example, operators of the process may experiment with repositioning or reorienting the electrode, the workpiece, or a baffle separating the electrode from the workpiece, or may modify aspects of a fluid flow within the reaction chamber in attempts to improve the level uniformity achieved by the process.
In a multiple-electrode reaction chamber, two or more electrodes are arranged in some pattern. Each of the electrodes is connected to an electrical power supply that provides the electrical power used to execute the electrochemical processing operations. Preferably, at least some of the electrodes are connected to different electrical nodes so that the electrical power provided to them by the power supply may be provided independent of the electrical power provided to other electrodes in the array.
Electrode arrays having a plurality of electrodes facilitate localized control of the electrical parameters used to electrochemically process the microelectronic workpiece. This localized control of the electrical parameters can be used to provide greater uniformity of the electrochemical processing across the surface of the microelectronic workpiece when compared to single electrode systems without necessitating hardware changes. However, determining the electrical parameters for each of the electrodes in the array to achieve the desired process uniformity can be problematic. Typically, the electrical parameter (i.e., electrical current, voltage, etc.) for a given electrode in a given electrochemical process is determined experimentally using a manual trial and error approach. Using such a manual trial and error approach, however, can be very time-consuming. Further, the electrical parameters do not easily translate to other electrochemical processes. For example, a given set of electrical parameters used to electroplate a metal to a thickness X onto the surface of a microelectronic workpiece cannot easily be used to derive the electrical parameters used to electroplate a metal to a thickness Y. Still further, the electrical parameters used to electroplate a desired film thickness X of a given metal (e.g., copper) are generally not suitable for use in electroplating another metal (e.g., platinum). Similar deficiencies in this trial and error approach are associated with other types of electrochemical processes (i.e., anodization, electropolishing, etc.). Also, this manual trial and error approach often must be repeated in several common circumstances, such as when the thickness or level of uniformity of the seed layer changes, when the target plating thickness or profile changes, or when the plating rate changes.
In view of the foregoing, a system for electrochemically processing a microelectronic workpiece that can be used to automatically identify electrical parameters that cause a multiple electrode array to achieve a high level of uniformity for a wide range of electrochemical processing variables (e.g., seed layer thicknesses, seed layer types, electroplating materials, etc.) would have significant utility.